Earlier this month Professor S. Settar from India's National Institute of Advanced Studies warned that the ring might be hidden from public view if it was sold to a private bidder.

He urged the Indian government to "make use of all available avenues, legal and diplomatic, to recover the ring".

If the ring could not be stopped from going to auction, he said, Indian philanthropists should be encouraged to purchase it on behalf of the nation. It is not known if the new owner of the ring is Indian.

Another group calling itself the Tipu Sultan United Front also urged Indian authorities to do all they could to prevent the ring from being sold.

The ring was previously listed for sale by Christie's in 2012 but was then withdrawn from sale.